The present invention relates to an apparatus allowing the photoactivation of photosensitive composites used especially in the dental field.
In the dental field, the composites consist of a photocurable resin which reacts to light by modification of its molecular layers or by thermal transformation of its molecules. These two phenomena, which may combine, are dependent on the wave length of the emitted radiation and also on the absorptivity of the composite and have the effect of activating its photoinitiators and of obtaining a substance having the mechanical properties and esthetic characteristics defined according to the dental application.
Photocuring apparatuses generally consist of a case containing an emitting source controlled by an electronic circuit which includes a timer allowing the exposure time to be optimized so as to minimize the heat-up of the tissues surrounding the region to be treated. Moreover, in order to be certain of covering the photosensitive spectral range of the material used and of delivering enough energy to the reaction, these apparatuses use lamps whose emission spectrum is very wide, in combination with filters.
Among the various light sources, mercury vapor lamps have been used, but these emit too much ultraviolet radiation which is dangerous to the patient""s eyes.
To avoid this drawback, these lamps have been replaced with halogen lamps. However, these lamps, the lumen/watt ratio of which is low, require the area: to be treated to be exposed for a long period, forcing the patient to keep his mouth open for a long time. Moreover, this overexposure is accompanied by the lamp heating up, requiring the use of noisy and bulky cooling systems.
To remedy these drawbacks, plasma arc lamps having a better lumen/watt efficiency are used at the present time, and part of their spectrum, between 430 and 490 nm, is used, thereby making it possible to significantly increase the energy delivered and to have the required power for rapid curing. However, this increase, in the power is accompanied by a strong increase in the heat dissipated.
In the apparatuses known to date, firstly the conversion of the electrical energy into light energy is mediocre and secondly the cooling systems are noisy and complex, thereby increasing the cost of the apparatus.
Document JP 07240536 describes a light source for a photocuring apparatus consisting firstly of light-emitting diodes which emit radiation between 380 nm and 430 nm and secondly of a concentrating device comprising optical fibers, opposite the entry face of each of which one of said diodes is placed.
However, the concentrating device of this type of apparatus does not allow optimum concentration of the light emanating from the diodes to be achieved since the latter are provided with a lens and because the fiber is in contact with this lens, so there is rapid curing of the materials because of poor coupling between said diodes and the optical fibers.
The object of the present invention is to remedy these drawbacks by proposing an apparatus for photocuring composites and substances for the whitening of teeth, making it possible to carry out rapid and gradual photocuring of the various layers of the material to be treated while allowing the heat dissipated to be significantly reduced.
The photocuring apparatus according to the invention is of the type comprising a case containing a power supply unit electrically controlled by a central electronic processing unit, a light source connected to the supply consisting of a matrix of light-emitting diodes and a device for concentrating the light emanating from the diodes, and is essentially characterized in that:
in a first embodiment, the concentrating device makes it possible to juxtapose, at a given concentration point, the light emanating from all the emitting surfaces of the diodes and consist of optical fibers associated with the light-emitting diodes so that the emitting area of a diode is optically matched as far as possible with the entry area of one or more corresponding optical fibers;
in a second embodiment of the invention, the device for concentrating the light emanating from the diodes makes it possible to superpose, at a given concentration point, the images of all the emitting surfaces of the diodes and consists, on one side, of a collimation device composed of a plurality of convergent lenses each placed in front of the emitting surface of a light-emitting diode in such a way that the emitting surface is at the object focus of the corresponding lens and in such a way that the rays are refracted parallel to the axis of the latter and, on the other side, a focusing device formed from a convergent lens of suitable dimensions in order to allow the parallel incident rays emanating from the collimation device to be refracted toward the concentration point which is the focus of the lens.
The collimating or focusing lenses may be of the refractive, diffractive (Fresnel lenses, holographic, binary lenses) or stepped-index type, or a combination of these various types of lenses. The focusing lenses will preferably be of the reflective type.
The given point where the light emanating from the diodes at the exit of the concentrating device is concentrated may be the entry face of a waveguide provided with an endpiece for applying the light coming from the light source to the region to be treated or it may be, directly, the region to be treated.
According to the invention, the diodes are optically matched as far as possible with the corresponding fiber or fibers by positioning the entry surface of the corresponding fiber in contact with the emission surface of the diode or in the immediate vicinity of the latter and by maintaining a ratio between the emitting area of the diode and the entry area of the fiber or fibers facing it as close as possible to 1.
The optical matching may also be accomplished by forming the image via an imaging optic which images the emissive area of the diode onto the entry face of one or more fibers, while keeping an area ratio as close as possible to 1.
In a preferred embodiment of the concentrating device consisting of optical fibers, the diodes are arranged in a regular manner on a plate and the optical fibers are each inserted into a hole having a diameter slightly greater than the diameter of said fibers and made in a plate positioned by alignment means near the support plate for the diodes and the pitch of the holes of which is equal to that of said diodes.
According to an additional feature of the invention the supply to the light-emitting diodes may be controlled manually by means of control knobs or automatically by means of the central processing unit containing in its memory the parameters inherent to the control of said diodes making it possible to obtain various power profiles.
According to another additional feature of the invention, the power supply to the diodes can be regulated in pulsed mode so as to obtain higher instantaneous powers, this being favorable for particular curing applications.
According to another additional feature of the invention, the light output by the bundle of optical fibers has at least two wavelengths lying preferably around 380 or 475 xcexcm and 750 xcexcm, so as to obtain both radiation necessary for certain composites and radiation suitable for thermal action on the substances intended for the whitening of teeth.
According to another additional feature of the invention, the core of the optical guide in which the light output by the concentrating device propagates may be made of plastic, of glass or it may be liquid.